On the surfaces of domestic electric products, writing materials or interior articles for a motor vehicle, crimps are applied for the various purposes such as an improvement of an outward appearance or a tactile impression, a prevention of glare, a prevention of slip or the like. As patterns of the crimps, are used patterns of various microscopic forms such as a skin, a woody texture, a rocky surface, a sandy texture, a crepe texture, a geometric pattern.
In order to form these crimps on the surfaces of the resin products, in place of a usual etching method or an electro-casting method, JP-A-7-241909 or JP-A-2004-358662 proposes a technique that treatment data is used to apply the crimps which is formed in such a way that depth of a surface configuration is converted to image data represented by the densities of 256 gradations from surface measured values obtained by reading the surface configuration of a skin model to form the treatment data by a computer.
When the treatment data is formed from crimp shaped data, in order to avoid a skew-ness from arising in the crimps in an inclined surface of a three-dimensional object, for instance, modeling soft is provided which uses a box cell data conversion that box cells are stacked on curved surfaces of the product in accordance with the densities corresponding to the depths of the crimps in the image data to form the crimps in a normal direction of the surface of the product.
However, in such a system, initially to convert product shaped data to box cell data, an enormous quantity of data is necessary.
Further, to the surface of the product having a continuous and complicated configuration including a plurality of curved surfaces, the crimp is formed for each of divided ranges, and after the crimp is formed, a process for a joint to an adjacent crimp form is necessary. However, a satisfactory process thereto is not yet unsolved.
Namely, it is difficult to adapt the crimps of the joint to the same form. In order to prevent the joint from outstanding, an amendment by a manual operation is necessary which requires a large number of processes. Further, since the amendment by the manual operation deforms the crimp forms to be joined together, a workmanship changes depending on the skill of an operator. Thus, an angular part is rounded and a groove or a crest is thickened or bent, so that the amendment may frequently deviate from an aim of the amendment to deteriorate an outward appearance and a quality is not stabilized. Accordingly, the fact is that an object to which the usual method is mainly applied is limited to a plane or a cylindrical surface.